Division of Materia Medica, Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing, Jiangsu 210042, China.

Introduction Acne vulgaris is a chronic inflammatory skin disease that affects 38.0% of adolescents aged 15��19 years and 36.0% of 20��24 years old in China[1]. It is a disease of the pilosebaceous unit that results in in-flammatory and noninflammatory lesions. The four principal pathological factors involved in the develop-ment of acne are sebum overproduction, follicular hyperkeratinization, abnormal proliferation of Propionibacterium acnes (P. acnes) within the follicle, and inflammation[2]. Acne requires long-term manage-ment, and its treatment is challenging, especially considering the disease chronicity and relapses, and the variability in response to treatments. Among the available topical treatments, antibiotics (erythromycin, clindamycin), azelaic acid, benzoyl peroxide (BPO), and retinoids (tretinoin, isotretinoin, and adapalene) are the most frequent choices. However, treating acne with antibiotics has increased the antibiotic resistance of P. acnes and other bacteria[3]. Additionally, current topical acne treat-ments often cause skin irritation, dryness, peeling, and other undesirable side effects that might limit patient compliance and reduce medical effectiveness. Because of the development of side effects and bacterial resistance to topical acne treatments, it is necessary to develop alternatives that are safe, effective, and well-tolerated.